Irregular surface drill rod for a directional drilling machine

ABSTRACT

A horizontal drilling machine for directionally drilling a drill string into the ground. The drill string includes a plurality of elongated members threaded together in an end-to-end relationship. The drilling machine includes a track, a rotational driver mounted on the track, and a thrust mechanism for propelling the rotational driver along the track. The rotational driver is used to rotate the drill string in forward and reverse directions about a longitudinal axis of the drill string. The drill string is rotated in the forward direction to thread the elongated members together, and rotated in the reverse direction to unthread the elongated members from one another. Rods of the drilling machine have surface irregularities for mixing or agitating drilling fluid within the bore.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 60/226,608, filed on Aug. 21, 2000.

FIELD OF THE INVENTION

[0002] The present invention relates generally to underground drilling machines. More particularly, the present invention relates to drill rod, of the type used in connection with a directional drilling machine. More particularly still, the present invention relates to a drill rod having an irregular surface for agitating drilling fluid, the drill rod for use in connection with an underground drilling machine in a horizontal directional drilling environment.

BACKGROUND OF THE INVENTION

[0003] Utility lines for water, electricity, gas, telephone and cable television are often run underground for reasons of safety and aesthetics. Sometimes, the underground utilities can be buried in a trench that is subsequently back filled. However, trenching can be time consuming and can cause substantial damage to existing structures or roadways. Consequently, alternative techniques such as horizontal directional drilling (HDD) are often used.

[0004] A typical horizontal directional drilling machine includes a drive mechanism slidably mounted on a frame. The movement of the drive mechanism is generally along the longitudinal axis of the frame. The drive mechanism is arranged and configured to rotate a drill string about the longitudinal axis of the drill string. Sliding movement of the drive mechanism along the frame, in concert with the rotation of the drill string, causes the drill string to be longitudinally advanced into or withdrawn from the ground.

[0005] In a typical horizontal directional drilling sequence, the horizontal directional drilling machine drills a hole into the ground at an oblique angle with respect to the ground surface. During drilling, a drilling fluid can be pumped through the drill string, over/about a drill head (e.g., a cutting or boring tool) mounted at the distal end of the drill string, and back up through the hole to remove cuttings and dirt. After the drill head reaches a desired depth, the drill head is then directed along a substantially horizontal path to create a horizontal hole. After the desired length of hole has been drilled, the drill head is then directed upwards to break through the ground surface. A reamer is then attached to the drill string which is pulled back through the hole, thus reaming out the hole to a larger diameter. It is common to attach a utility line or other conduit to the drill string so that it is dragged through the hole along with the reamer.

[0006] To drill relatively long holes, drill strings may include many interconnected lengths of drill pipe. The individual pieces of pipe are typically threaded together to form the drill string. During drilling operations, the drill string is typically rotated in a forward direction (e.g., clockwise). Thus, assuming the pipes have right-hand threads, the forward rotation of the drill string encourages the pipes to remain threaded together. Although at other times it may be desirable to rotate the drill string in a reverse direction (e.g., counterclockwise).

[0007] There are instances in which the drill string includes physical structures to perform various functions. For example, U.S. Pat. No. 5,060,736 generally discloses a series of concentric stabilizers. The stabilizers are used to position the drill string relative to the cutting bit. Also, U.S. Pat. No. 5,649,603 generally discloses a series of roller stabilizer type devices which tend to convert rotary contact to a longitudinal force. It will be appreciated, however, that in most cases the exterior surface of the drill rod is smooth.

[0008] In order to bring the spoils back along the length of the drill string from the distal end and out of the hole at the proximal end, a cutting fluid is generally used. Since both fluid flow and rotation of the drill string is interrupted while adding or removing lengths of drill pipe to the drill string, the cutting fluids generally used are viscous to help keep the spoils in suspension. However, there are disadvantages to use of viscous fluids. For examples, such fluids may be disadvantageous to the environment or with longer distance holes, a more viscous fluid may introduce undesired hole pressure. Under certain conditions, excessive hole pressure results in the ground breaking open at an unintentional location and drilling fluid is lost through the unintentional hole. This event is sometimes termed “fracking” in the industry.

[0009] Therefore, there arises a need for a drill rod which is capable of keeping spoils in suspension and/or to re-suspend spoils while the drill string is being longitudinally rotated. The drill string may also optionally be used with a less viscous fluid and keep the spoils in suspension (or re-suspend upon rotation of the drill string during operation) over longer distances. The present invention provides for this and other advantages.

SUMMARY OF THE INVENTION

[0010] The present invention provides a simple and reliable method and apparatus for automatically, and continuously during operation, helping maintain spoils in suspension while being transported to the surface in a drilling environment. By keeping the spoils in suspension, the hole being dug may be kept cleaner, a longer hole may be dug, and/or a lower viscous fluid may be used.

[0011] In a preferred embodiment of the present invention, an irregular surface is provided on the drill rod which comprises a drill string in a horizontal drilling environment (and more particularly in a horizontal directional drilling (HDD) environment). The irregular surface may be defined to include open grooves or channels (square or rounded), scalloped sections, concave sections, and/or other complex angle sections. The irregular surface may be arranged and configured generally parallel to the longitudinal axis of the drill rod or may be generally spiraled around the longitudinal axis of the drill rod.

[0012] One feature of the present invention is that the interaction of the irregular surface with the mud/particles (e.g., spoils) contained in the drilling fluid causes the spoils to remain in suspension for longer distances. Further, a less viscous fluid may be utilized, thereby decreasing hole pressure and the possibility of fracking.

[0013] It will be appreciated that an HDD environment is one of several in which the present invention may be employed. For example, the principles of the present invention might also be employed in other long hole drilling environments, such as vertical drilling.

[0014] One aspect of the present invention relates to a drill rod including a length of elongated material. An irregular surface is provided on the exterior of the elongated material. The irregular surface defines an effective outer circumference, and a lowered area recessed relative to the effective outer circumference.

[0015] While the invention will be described with respect to various preferred embodiment configurations and with respect to a particular type of drilling environment, it will be understood that the invention is not to be construed as limited in any manner by such configurations and representative environments described herein. The principles of the present invention apply to the use of an irregularly structured surface of the drill rod in a drill string so as to keep the spoils in suspension, or to re-suspend the spoils upon actuation of rotation of the drill rod, during drilling operation. By keeping the spoils in suspension and/or re-suspending the spoils, a lower viscous fluid may be used, the hole may be cleaner, and/or the spoils may travel over longer distances.

[0016] These and various other advantages and features which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages and objectives obtained by its use, reference should be had to the drawings which form a further part hereof and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate several aspects of the invention and together with the description, serve to explain the principles of the invention. A brief description of the drawings is as follows:

[0018]FIG. 1 shows a horizontal directional drilling machine constructed in accordance with the principles of the present invention;

[0019]FIG. 2 shows a schematic threaded connection formed between two elongated members that form the drill string shown in FIG. 1;

[0020]FIG. 3a shows a perspective view of a first embodiment of the present invention;

[0021]FIG. 3b shows a side elevation view of the first embodiment shown in FIG. 3a;

[0022]FIG. 3c shows a cross section view taken through line B-B of FIG. 3b;

[0023]FIG. 3d shows a cross section view taken through line A-A of FIG. 3b;

[0024]FIG. 4a shows a perspective view of a second embodiment of the present invention;

[0025]FIG. 4b shows a side elevation view of the second embodiment shown in FIG. 4a;

[0026]FIG. 4c shows a cross section view taken through line B-B of FIG. 4b;

[0027]FIG. 4d shows a cross section view taken through line A-A of FIG. 4b;

[0028]FIG. 5a shows a perspective view of a third embodiment of the present invention;

[0029]FIG. 5b shows a side elevation view of the third embodiment shown in FIG. 5a;

[0030]FIG. 5c shows a cross section view taken through line B-B of FIG. 5b;

[0031]FIG. 5d shows a cross section view taken through line A-A of FIG. 5b;

[0032]FIG. 6a shows a perspective view of a fourth embodiment of the present invention;

[0033]FIG. 6b shows a side elevation view of the fourth embodiment shown in FIG. 6a;

[0034]FIG. 6c shows a cross section view taken through line B-B of FIG. 6b;

[0035]FIG. 6d shows a cross section view taken through line A-A of FIG. 6b;

[0036]FIG. 7a shows a perspective view of a fifth embodiment of the present invention;

[0037]FIG. 7b shows a side elevation view of the fifth embodiment shown in FIG. 7a;

[0038]FIG. 7c shows a cross section view taken through line B-B of FIG. 7b; and

[0039]FIG. 7d shows a cross section view taken through line A-A of FIG. 7b.

DETAILED DESCRIPTION

[0040] With reference now to the various drawing figures in which identical elements are numbered identically throughout, a description of various exemplary aspects of the present invention will now be provided.

[0041] As mentioned above, the principles of this invention apply to the use of an irregularly structured surface of the drill rod in a drill string so as to keep the spoils in suspension, or to re-suspend the spoils upon actuation of rotation of the drill rod, during drilling operation. By keeping the spoils in suspension and/or re-suspending the spoils, a lower viscous fluid may be used, the hole may be cleaner, and/or the spoils may travel over longer distances. A preferred application of the present invention is in an HDD environment.

[0042] In order to facilitate a better understanding of the present invention, a detailed discussion of the drill pipe will be deferred pending a brief discussion of an HDD environment and the directional drilling machine with which the drill pipe might be used.

[0043] Turning first to FIG. 1, a typical directional drilling machine 10 is illustrated. The drilling machine 10 is adapted for pushing a drill string 14 into the ground 16, and for pulling the drill string 14 from the ground 16. The drill string 14 includes a plurality of elongated members 14 a and 14 b (e.g., rods, pipes, etc.) that are connected in an end-to-end relationship. A drill head 28 is preferably mounted at the far end of the drill string 14 to facilitate driving the drill string 14 into the ground 16. The dill head 28 can include, for example, a cutting bit assembly, a starter rod, a fluid hammer, a sonde holder, as well as other components.

[0044] Preferably, each of the elongated members 14 a and 14 b includes a threaded male end 18 (best seen schematically in FIG. 2) positioned opposite from a threaded female end 20 (shown in FIG. 2). These ends are often respectively termed the pin end (18) and the box end (20). To couple the elongated members 14 a and 14 b together, the male end 18 of the elongated members 14 a is threaded into the female end 20 of the elongated member 14 b to provide a threaded coupling or joint.

[0045] Referring again to FIG. 1, the directional drilling machine 10 includes an elongated guide or track 22 that can be positioned by an operator at any number of different oblique angles relative to the ground 16. A rotational driver 24 is mounted on the track 22. The rotational driver 24 is adapted for rotating the drill string 14 in forward and reverse directions about a longitudinal axis 26 of the drill string 14. As used herein, the terms “forward direction” or “forward torque” are intended to mean that the drill string is rotated in a direction that encourages the elongated members 14 a and 14 b to thread together. For example, if the elongated members 14 a and 14 b have right-hand threads, the forward direction of rotation or torque is in a clockwise direction. By contrast, the terms “reverse direction” or “reverse torque” are intended to mean that the drill string is rotated in a direction that encourages the elongated members 14 a and 14 b to unthread from one another. For example, if the elongated members 14 a and 14 b include right-hand threads, the reverse direction or reverse torque is oriented in a counterclockwise direction.

[0046] As shown in FIG. 1, the rotational driver 24 includes a gear box 30 having an output shaft 32 (i.e., a drive chuck or a drive shaft). The gear box 30 is powered by one or more hydraulic motors 34. As depicted in FIG. 1, two hydraulic motors 34 are provided. However, it will be understood that more or fewer motors 34 can be coupled to the gear box 30 depending upon the amount of torque that is desired to be generated by the rotational driver 24. While a hydraulic system has been shown, any number of different types of devices known for generating torque could be utilized. For example, in alternative embodiments, an engine such as an internal combustion engine might be used to provide torque to the drill string 14.

[0047] The rotational driver 24 is adapted to slide longitudinally up and down the track 22. For example, the rotational driver 24 can be mounted on a carriage (not shown) that slidably rides on rails (not shown) of the track 22 as shown in U.S. Pat. No. 5,941,320. Such patent is hereby incorporated herein and made a part hereof by reference. A thrust mechanism 40 is provided for propelling the rotational driver 24 along the track 22. For example, the thrust mechanism 40 moves the rotational driver 24 in a downward direction (indicated by arrow 42) to push the drill string 14 into the ground 16. By contrast, the thrust mechanism propels the rotational driver 24 in an upward direction (indicated by arrow 44) to remove the drill string 14 from the ground 16. It will be appreciated that the thrust mechanism 40 can have any number of known configurations. As shown in FIG. 1, the thrust mechanism 40 includes a hydraulic cylinder 46 that extends along the track 22. The hydraulic cylinder 46 is coupled to the rotational driver 24 by a chain drive assembly (not shown). Preferably, the chain drive assembly includes a chain that is entrained around pulleys or gears in a block and tackle arrangement such that an incremental stroke of the hydraulic cylinder 46 results in an increased displacement of the rotational driver 24. For example, in one particular embodiment, the chain drive assembly displaces the rotational driver 24 a distance equal to about twice the stroke length of the hydraulic cylinder 46. Directional drilling machines having a chain drive arrangement as described above are well known in the art. For example, such chain drive arrangements are used on numerous directional drilling machines manufactured by Vermeer Manufacturing Company of Pella, Iowa.

[0048] While one particular thrust arrangement for moving the rotational driver 24 has been described above, any number of different configurations can be used. For example, one or more hydraulic cylinders can be coupled directly to the rotational driver 24. Alternatively, a rack and pinion arrangement could also be used to move the rotational driver 24. Furthermore, a combustion engine or simple chain or belt drive arrangements, which do not use hydraulic cylinders, could also be used.

[0049] Referring still to FIG. 1, the drilling machine 10 further includes upper and lower gripping units 50 and 52 for use in coupling and uncoupling the elongated members 14 a and 14 b of the drill string 14. The upper gripping unit 50 includes a drive mechanism 54 (e.g., a hydraulic cylinder) for rotating the upper gripping unit 50 about the longitudinal axis 26 of the drill string 14. The gripping units 50 and 52 can include any number of configurations adapted for selectively preventing rotation of gripped ones of the elongated members 14 a and 14 b. For example, the gripping units 50 and 52 can be configured as vice grips that when closed grip the drill string 14 with sufficient force to prevent the drill string 14 from being rotated by the rotational driver 24. Alternatively, the gripping units 50 and 52 can include wrenches that selectively engage flats provided on the elongated members 14 a and 14 b to prevent the elongated members from rotating.

[0050] To propel the drill string 14 into the ground 16, the rotational driver 24 is positioned at an uppermost location (shown in FIG. 1), and the drill head 28 is gripped within the lower gripping unit 52. The elongated member 14 a is then placed in axial alignment with the output shaft 32 of the rotational driver 24 and the drill head 28. Once alignment has been achieved, the rotational driver 24 rotates the output shaft 32 in a forward direction. This causes the shaft 32 to thread into the female threaded end 20 of the elongated member 14 a, and the male threaded end of the elongated member 14 a to concurrently thread into the female threaded end of the drill head 28. The drill head 28 is prevented from rotating by the gripping unit 52. During the threading process, the rotational driver 24 advances downward to ensure that the lower end of the elongated member 14 a contacts the drill head 28 and the upper end of the elongated member 14 a contacts the output shaft 32. Preferably, the forward torque provided by the rotational driver 24 is limited by a torque limiter to ensure that the drive shaft 32 exceed a predetermined torque. The forward torque used to provide the threaded connection between the drive shaft 32 and the elongated member 14 a is called the “make-up torque.”

[0051] After the first elongated member 14 a has been coupled to the drive shaft 32 and the drill head 28, the lower gripping unit 52 releases the elongated member 14 a and the rotational driver 24 is propelled in a downward direction along the track 22 such that the elongated member 14 a is pushed into the ground 16. As the elongated member 14 a is pushed into the ground 16, the rotational driver 24 preferably rotates the elongated member 14 a such that the drill head 28 provides a boring or drilling action. After the elongated member 14 a has been fully pushed into the ground 16, the trailing end of the elongated member 14 a is gripped by the lower gripping unit 52 to prevent rotation of the elongated member 14 a. Once the trailing end of the elongated member 14 a has been gripped by the lower gripping unit 52, the rotational driver 24 applies a reverse torque to the drive shaft 32 to break the joint formed between the drive shaft 32 and the elongated member 14 a.

[0052] Once the joint has been broken, the drive shaft 32 is completely unthreaded from the elongated member 14 a, and the rotational driver 24 is moved upward along the track 22 to the uppermost position (e.g., the position shown in FIG. 1). Next, the elongated member 14 b is placed in alignment with the elongated member 14 a and the drive shaft 32, and the sequence described above is repeated. Thereafter, depending upon the length of the hole it is desired to drill, additional elongated members can be added to the drill string in the same manner described above.

[0053] As the drill string 14 is advanced into the hole, the spoils are generally carried out of the hole by a drilling fluid. As the drill string 14 is made up or broken down, rotation of the drill string at least momentarily ceases.

[0054] Drilling fluid may also be used to cool and/or lubricate the cutting head, and provide for a cutting action through the ground at the front of the cutting head, in addition to helping bring the spoils back along the hole being drilled and out of the hole (e.g., from the distal end to the proximal end, e.g., the proximal end is generally the entry point for the drill string into the earth). In some instances (e.g., percussive head environments), the drilling fluid can be delivered under pressure to the drill head in order to provide power transfer to the active portion of the drill. The drill liquid can comprise aqueous and non-aqueous fluids (e.g., drilling fluid solutions, dispersions or muds). Such fluids can include aqueous and non-aqueous liquids which can be formulated with additives for a variety of useful properties.

[0055] Existing aqueous based liquids may include water solutions or dispersions with certain types of materials, such as a synthetic polymer material or a natural or synthetic clay, that are known to have expansion and lubricating characteristics, for example, a bentonite. Other aqueous based liquids that may be used include water based drilling fluids containing CaO, CaCO₃, lime and potassium compounds and similar inorganic materials. Fluids can incorporate small amounts of polymeric materials including preferred unmodified polymeric additives and sulfonated polymers such as styrene-maleic anhydride copolymer and at least one water-soluble polymer prepared from acrylic acid, acrylamide or their derivatives. Still other aqueous drilling fluids include water combined with gelling agents, defoamers and glycerines selected from the group consisting of glycerine, polyglycerine and mixtures thereof. Others include invert emulsion drilling fluids. Polymeric based fluids can be formulated with organic or carbohydrate thickeners including, for example: cellulose compounds, polyacrylamides, natural galactomannans and various other polysaccharides.

[0056] Existing non-aqueous based liquids can include synthetic fluids including polyglycols, synthetic hydrocarbon fluids, organic esters, phosphate esters and silicones. It is to be understood, however, that aqueous and non-aqueous based liquids are not limited to those recited above. Those skilled in the art will recognize that other liquids may be used for drilling fluids.

[0057] It will also be appreciated that by keeping the mud/particle slurry (e.g., the combined spoils and drilling fluid) stirred up, the spoils will travel further along the bore path to the surface of the drilling operation. The use of the irregular surface drill pipe helps keep the hole clean and may provide an opportunity to use a less viscous fluid. The use of a less viscous fluid may in turn lead to fewer pumping problems. While higher viscosity fluids are currently used to move spoils longer distances, such fluids present problems. For example, the higher viscosity mud causes hole pressure, which in turn generates fracking (i.e., where the ground breaks open unintentionally in a location remote from the entry hole of the drilling operation). When fracking occurs at the surface, drilling fluid is lost and the area where the fracking occurs may need treatment for environmental reasons. Accordingly, if a lower viscosity fluid is used, then the chances of fracking is reduced.

[0058] In FIGS. 3 through 7, five embodiments of the present invention are illustrated. In each embodiment, an irregular surface on the drill rod 14 a is shown. As noted above, such irregular surface may be defined to include open grooves or channels (square or rounded), scalloped sections, concave sections, and/or other complex angle sections formed in the surface of the drill rod 14 a. The irregular surface can also include fluted or lobed type/shaped cross sections. The irregular surface may be formed generally parallel to the longitudinal axis of the drill rod or may be generally spiraled around the longitudinal axis of the drill rod.

[0059] It will be appreciated that the design of the irregular surface preferably has outside edges which do not tend to impede the rotation of the drill rod in the hole (often termed “hanging in the hole”). Accordingly the outside radius of such sections define an effective outside circumference (i.e., the boundary which is defined by outermost portions of the drill rod and which traverses the surface irregularities) of the drill rod 14 a. It will be appreciated that the mean outside circumference is preferably circular, but could also be other shapes such as oblong, oval, elliptical, etc. Further, the strength of the drill rod 14 a may be impacted by the selected irregular surface shape(s). Those of skill in the art will appreciate that when designing such irregular surface shapes, the required structural strength of the drill rod must be kept in mind as well as the desired flexure of the rod and/or its elastic capabilities. In general, the drill rod is constructed of an alloy steel. However, other materials might be used. Still further, while drill rod 14 a is shown in connection with FIGS. 3-7, it will be appreciated that an irregular surface may be used on one, a plurality or all of the drill rods (14 a, 14 b, etc.) which make up the drill string 14.

[0060] Other design considerations for the irregular surface(s) may include details which impact the interaction between the irregular surface and the spoils during: 1) a constant rotation of the drill string 14 (e.g., during a drilling phase of the operation and/or a back-reaming phase); and 2) a start-up phase after a make-up or break down phase of drilling (e.g., as rotation begins after adding or taking away a section of the drill rod 14 a from the drill string 14). Since drill rod rotation and fluid circulation is discontinued to begin disassembly of the rod joint on the surface for either rod removal or rod insertion, the particles in the hole have a tendency to quickly settle. However, the use of the irregular surface causes an agitation effect in the hole to re-lift the spoils into the transport/drilling fluid. The fluid continues to be agitated during rotation until the drilling fluid reaches the drilling entry hole at the surface (or in the entry/exit pit, if used). Use of such irregular surface does not change the method or mode of drilling operation—other than the benefits which may be obtained by its use.

[0061] Each of FIGS. 3-7 include a perspective as FIG. “a”, a side elevation as FIG. “b”, a longitudinal cross section as FIG. “c”, and a transverse cross section as FIG. “d”. Common components between the different embodiments will not be discussed in connection with FIGS. 4 through 7.

[0062] Turning now to FIGS. 3a-3 d, a drill rod 14 a is illustrated having a longitudinal axis along the line designated at 101. Internal shoulders 103 and 105 provide structural strength to the male (pin) end 18 and female (box) end 20 respectively. A groove or channel 100 is defined in the outer shell 104 of the drill rod 14 a. The channel 100 is defined by a surface irregularity or lowered area that is recessed relative to an effective outer circumference defined by an outermost surface 102 of the rod 14 a. In the embodiment illustrated in FIGS. 3a-3 d, the groove/channel is shown as being rounded in cross section. However, it will be appreciated that a square cross section (or other more sharply angled) profile might be used. For example, the groove may be configured such that the periphery of the groove may form more of a right angle with respect to a tangent to the outermost surface 102 of the drill rod 14 a.

[0063] The groove or channel 100 is formed in a pattern which is spiraled or twisted about the longitudinal axis 101 of the drill rod 14 a. It is believed that this configuration may help provide an auger like effect which further helps transport the spoils from the cutting head 28 (the distal end) back to the hole opening (the proximal end) when the drill string 14 is rotated in the appropriate direction. However, it should be understood that such grooves 100 might be generally aligned with the longitudinal axis 101 of the drill rod 14 a (e.g., as illustrated with respect to FIGS. 5a-5 d).

[0064]FIGS. 4a-4 d illustrate a second embodiment similar to the first embodiment. The exception is that the grooves are more closely spaced. More specifically, there are four (4) grooves 100 illustrated in FIGS. 3a-3 d spaced approximately ninety (90) degrees about the effective outer circumference 150 of the drill rod 14 a. In FIGS. 4a-4 d, there are six (6) grooves 100 spaced approximately sixty (60) degrees about the effective outer circumference 150 of the drill rod 14 a. It will be appreciated that other numbers of grooves 100 might be used.

[0065]FIGS. 5a-5 d illustrate a third embodiment. In this embodiment, the irregular surface is comprised of a more “lobed” cross-section profile. More specifically, four grooves 106 are oriented generally parallel with the longitudinal axis 101 and are spaced approximately equidistant from one another about the effective outer circumference 150 of the drill rod 14 a. The grooves 106 are separated by lobes 155. Outer surfaces 102 of the lobes 155 define the effective outer circumference 150. The grooves 106 provide for a lowered area relative to the effective outer circumference 150. The curve of the leading and trailing edges 120 a and 120 b differ from one another. The angle θ₁ formed between 120 b and a normal to the effective outer circumference 150 is smaller than the angle θ₂ formed between 120 a and a normal to the effective outer circumference 150. Accordingly, the profile at 120 a may be termed shallower and the profile at 120 b may be termed steeper. The difference in the angles provides for a mixing action with the steeper angle and less chance for hanging up between the shallower angle and the drilled hole as the rod 14 a rotates. In this embodiment, although the internal surface or periphery 107 is shown as having a lobed cross section profile, it will be appreciated that such profile may also be circular or more generally circular.

[0066]FIGS. 6a-6 d illustrate a fourth embodiment. In this embodiment, the irregular surface is comprised of a lobed pattern 109 which is similar to the surface of the third embodiment. However, the leading and lagging profiles of the lobed pattern 109 are more equal to one another. Also, the internal profile 108 differs from profile 107. Further, the internal shoulders 103 and 105 are more pronounced and taper from the larger diameter to a smaller diameter as the shoulders approach the ends of the drill rod 14 a. As noted above, the strength of the rod 14 a, as well as the desired torsional and flexure characteristics, will help determine the actual designed profiles.

[0067]FIGS. 7a-7 d illustrate a fifth embodiment 158. In this embodiment, the irregular surface includes a plurality of depressions 159 separated by lobes 160. Outermost portions or points 162 of the lobes 160 define the effective outer circumference 150 of the rod. The depressions 159 extend longitudinally along the length of the rod in a helical or spiral pattern. For clarity, this embodiment does not show a pin or box located at the ends, but it will be appreciated that these structures can be provided. Also, the number and pitch of the lobes can be varied.

[0068] Those of skill in the art will appreciate that in each of the embodiments illustrated in FIGS. 3-7, the irregular surface comprises a lowered area formed in the outer shell of material 104 and open to the effective outer circumference 150 of the drill rod 14 a. The outer shell 104 is that structure of the drill rod 14 a between the inner periphery (which defines the void running the longitudinal length of the rod 14 a ) and the outermost surface 102. Since the outermost surface 102 or portion of the drill rod 14 a is interrupted by the irregular surface, an “effective” outer circumference is formed.

[0069] With regard to the forgoing description, it is to be understood that changes may be made in detail, especially in matters of the construction materials employed and the size, shape and arrangement of the parts without departing from the scope of the present invention. It is intended that these specific and depicted aspects be considered exemplary only, with a true scope and spirit of the invention be indicated by the broad meaning of the following claims. 

What is claimed is:
 1. A drill rod, of the type used in a drilling operation, the drill rod comprising: a) a length of elongated material having a first end and a second end; b) an inner periphery forming a void between the first end and the second end of the elongated material; and c) an irregular surface on the exterior of the elongated material, the irregular surface defining an effective outer circumference and a lowered area recessed relative to the effective outer circumference.
 2. The drill rod of claim 1, wherein the irregular surface includes a series of channels.
 3. The drill rod of claim 1, wherein the irregular surface includes a series of lobes.
 4. The drill rod of claim 1, wherein the elongated material has a longitudinal axis and wherein the irregular surface is arranged and configured into a spiral pattern about the longitudinal axis.
 5. The drill rod of claim 1, wherein the elongated material has a longitudinal axis and wherein the irregular surface is arranged and configured into one or more lines which are generally parallel to the longitudinal axis.
 6. The drill rod of claim 2, wherein the channels have a rounded cross-section profile.
 7. The drill rod of claim 3, wherein the cross section profile of the lobes includes a leading edge and a trailing edge.
 8. The drill rod of claim 7, wherein the profile of the leading and the trailing edges are identical.
 9. The drill rod of claim 7, wherein the profile of the leading and trailing edges differ.
 10. The drill rod of claim 1, wherein the inner periphery has a generally circular cross-section profile.
 11. The drill rod of claim 1, wherein the inner periphery has a generally lobed cross-section profile.
 12. A drill rod for a horizontal drilling machine for directionally drilling a drill string into the ground, the drill string including a plurality of elongated members connected end-to-end and the horizontal drilling machine using a drilling fluid for helping transport spoils out of the hole in operation, the drill rod comprising: a) an inner periphery defining a void between a first and second end of the drill rod; b) an outer periphery including outermost portions defining an effective outer circumference of the drill rod; c) an irregular surface provided at the outer periphery which is recessed relative to the effective outer circumference; and d) wherein the irregular surface agitates the drilling fluid and spoils during operation, whereby the spoils remain suspended in the drilling fluid.
 13. A horizontal drilling machine for directionally drilling a drill string into the ground, comprising: a) a track; b) a rotational driver for rotating the drill string in forward and reverse directions about a longitudinal axis of the drill string; c) a thrust mechanism for propelling the rotational driver along the track; d) a plurality of drilling rods, the drilling rods including: i) an inner periphery defining a void between a first and second end of the drill rod; ii) an outer shell defining an effective outer circumference; iii) an irregular surface formed in the outer shell which is recessed relative to the effective outer circumference; and iv) wherein the irregular surface agitates the drilling fluid and spoils when the rotational driver is rotating the drill string, whereby the spoils remain suspended in the drilling fluid, and wherein the irregular surface agitates the drilling fluid and spoils to re-suspend the spoils when rotation begins after adding or removing a drill rod from the drill string.
 14. A method for directionally drilling a drill string into the ground, the drill string including a plurality of elongated members and having an inside and an outside, the drill string including outer surface irregularities, the method comprising: pushing the drill string into the ground; rotating the drill string by applying a torque to the drill string; pumping a drilling fluid on the inside of the drill string from the proximal end of the drill string to the distal end of the drill string; and agitating the drilling fluid on the outside of the rotating drill string with the surface irregularities to help keep the spoils suspended in the drilling fluid as the fluid flows back on the outside of the drill string from the distal end to the proximal end.
 15. A drill rod comprising: a hollow rod member having a threaded male end and a threaded female end; the hollow rod member including an outer surface defining at least one recess that extends at least partially in a longitudinal direction along the rod member.
 16. The drill rod of claim 15, wherein the at least one recess includes a plurality of recesses spaced about a circumference of the rod member.
 17. The drill rod of claim 16, wherein the recesses extend longitudinally along the rod member in a spiral pattern.
 18. The drill rod of claim 16, wherein the recesses comprise linear slots aligned parallel to a longitudinal axis of the rod member. 